The X-37B Orbital Test Vehicle (OTV) is the US Air Force's unmanned, reusable space plane. It is the newest and most advanced re-entry spacecraft. (File photo)

The US Air Force has announced plans to launch its secretive, unmanned spacecraft known as X-37B Orbital Test Vehicle (OTV) later this week to carry out “experimental operations.”

For the first time, the experimental space plane will be launched on September 7 aboard Elon Musk’s SpaceX Falcon 9 rocket, the Air Force announced in a statement cited in a Friday report by the US-based military.com news outlet.

Marking the fifth mission for the X-37B, the statement noted, the OTV “will also be launched into, and landed from, a higher inclination orbit than prior missions to further expand the X-37B’s orbital envelope.”

While the payloads and most activities of the robotic X-37B remain classified, the Air Force further noted that this mission will carry “the Air Force Research Laboratory Advanced Structurally Embedded Thermal Spreader (ASETS-II) payload to test experimental electronics and oscillating heat pipe technologies in the long-duration space environment.”

“The many firsts on this mission make the upcoming OTV launch a milestone for the program,” said Randy Walden, director of the Air Force Rapid Capabilities Office, which is responsible for the X-37B’s experimental operations.“It is our goal to continue advancing the X-37B OTV so it can more fully support the growing space community."

The United Launch Alliance, a joint venture between Boeing Co. and Lockheed Martin Corp., has launched the OTV’s previous four missions via its Atlas V rockets.

The unmanned spacecraft completed its fourth mission on May 7, 2017, landing after 718 days in orbit and extending its total number of days spent in orbit to 2,085, the air force noted.

The program hit a milestone during its fourth rotation on March 25 after the X-37B spent 675 days in orbit, surpassing its previous record of 674 days.